(1) Field of the Invention
The invention generally relates to an apparatus for performing mathematical analyses and particularly to a computer-based apparatus that provides graphical user interfaces.
(2) Description of the Prior Art
A primary limitation in acoustic array performance is flow noise induced by turbulent wall-pressure fluctuations which exist due to the moderate to high Reynolds number turbulent boundary layers on the arrays.
Methods aimed at boundary layer control are of limited effectiveness due to inherent fluid physics. Mitigation of flow noise is therefore accomplished through the mechanical design of the array.
Mechanical design is taken to include the supporting structure and the sensor specifications and configuration. Optimal mechanical design requires detailed knowledge of the turbulent boundary layer including the relevant length and time scales in the flow field. Sensor arrays are often designed to resolve particular wavenumber and frequency bandwidths. In order to assess a given design, a number of computations are required which historically have been done in an ad hoc fashion. In addition, simplifying assumptions are often made for convenience in performing the design and analysis.
Over the past thirty years, the use of boundary layer variables typically did not appear in the analysis, in part due to the fact that knowledge of the boundary layer variables is often lacking or difficult to obtain. Furthermore, high Reynolds number turbulent boundary layers in water have a wide range of energy-containing length and time scales. This range needs to be considered. However, many efforts have only focused attention on the low wavenumber portion of the pressure spectra. Though this region is clearly of interest, the dominant energy is contained in the convective ridge wavenumber region.
In addition to a detailed understanding of the turbulent boundary layer, semi-empirical models of the spectrum of the wall-pressure fluctuations are required. The solutions of these models require extensive iteration and numerical integration over frequency and wavenumber and as such can be cumbersome to utilize. Furthermore, the models (which include a limited number or no boundary layer parameters) are only approximate in nature.
The prior art includes analyses of such wall pressure fluctuations, for example as reported by W. L. Keith, et al., “A comparison of turbulent boundary layer wall-pressure spectra,” Journal of Fluids Engineering, 1992, Vol. 114, pp. 338-347.
The prior art also includes the Broadside Acoustic Noise Estimation (BANE) model that was developed by Dr. Lowell Brooks. This computer code is aimed primarily at towed array self-noise analysis and contains many empirical parameters. It is not predicated on detailed knowledge of turbulent boundary layer physics. It also does not have a graphical user interface, and cannot be used for the applications of experimental wall-pressure measurements or hull arrays without significant modification.
The prior art also includes other codes aimed at flow noise analysis. With the shift in research emphasis away from flow noise, most of these codes became inactive and are now somewhat outdated and are not readily available.
Also known in the prior art is Kim et al. (U.S. Pat. No. 6,151,680) which is said to disclose a design system associated with pre-stressed concrete cylinder pipe (PCCP) using a graphic user interface (GUI), which is capable of carrying out, a variety of operations such as the design of embedded-cylinder pipe, lined-cylinder pipes, and fittings, computer-aided drawing interfaces, operations for quantity calculation, operations for inquiry to a database, and operations for a demonstration presentation, in a GUI environment; thereby, allowing for the easy use of the design system by the user.
In accordance with this operating method, it is possible to not only reduce the time taken to design the above pipes, and fittings, but also to allow the user to achieve such a design even when there is no theoretical knowledge of that design while only having knowledge of data inputting and outputting.
Also known in the prior art is Keith et al. (U.S. Pat. No. 7,130,242) which is said to disclose a system and method for detecting an acoustic signal in the presence of flow noise produced by the turbulent flow field that develops about a hosewall of a towed array. Pressure is measured with sensors at two diametrically-opposed locations at the surface of the hosewall over a period of time. The sensed pressure signals are used to generate an ensemble-averaged cross-spectra which effectively cancels out the flow noise while retaining the acoustic signal associated with a possible target of interest.
Flow-induced vibrations impact towed array reliability by causing mechanical failure of connectors and components. As such, there is a need for systems and methods that provide the ability to quickly assess the impact of design changes in acoustic arrays in order to avoid towed array failures.